In order for rolling element bearings to operate in a reliable way, they have to be adequately lubricated. The main purpose of the lubricant is to prevent metallic contact between the rolling elements. The lubricant also protects bearing surfaces against corrosion.
Bearings can suffer damage when they are not rotating.
False-brinelling occurs in a bearing as a result of fretting and/or smearing occuring over time when the bearing is subject to alternating loads, whilst the bearing is not rotating. For example, where a component of a machine such as the blade of a wind turbine is supported in a bearing so that the component may rotate, and the component is subject to cyclic loading whilst the component is not rotating in the bearing.
These alternating loads cause small movements, fretting or smearing movements, between the raceways and the balls or rollers of the bearing which remove the lubrication film between the raceways and the balls or rollers, resulting in metal to metal contact causing surface defects leading to false brinelling. When the bearing is caused to rotate, premature failure is likely to occur.
False-brinelling is a longstanding problem and has been addressed in many ways. False-brinelling is commonly addressed by simply taking the preventitive measure of rotating the bearing periodically so that the lubrication film between the raceway and the balls or rollers is either not removed or is restored. However, there is no accurate method of determining the periodic cycle for rotating a bearing that would otherwise be static.
Structural vibration measurements and displacement measurements have been utilised to quantify false brinelling. However, because many other factors need to be taken into account these techniques often fail to predict false brinelling.
Vibration measurement may be used to detect the presence of false brinelling during rotation of the bearing, but at the point significant vibration occurs the bearing is already damaged.
It would be desirable to be able to predict accurately when false brinelling is likely to occur.
It would be desirable to be able to control a component of a machine mounted in a bearing such that the lubrication layer is restored prior to the occurence of false brinelling.